A power source, such as a power converter, may be used in a power system to provide substantially accurate voltage regulation for an electrical load. Often it may be desirable to provide such voltage regulation directly at the load. This regulation technique is generally referred in the art as point of load regulation. One example application may be a battery charger system where the load (e.g., a battery) may be temperature sensitive. Another example application that may involve sensitive loads may be a computer system.
The power converter supplies output current through one or more power lines to the load. In operation, the flow of current causes a voltage drop along the lines connected from the power converter to the load due to the impedance of the conducting lines. As noted above, it may be desirable to regulate the voltage at the point of load (as opposed to the power converter output) to provide accurate voltage regulation at the load. To account for the voltage drop across the power lines, the voltage at the converter output may be set relatively higher than the nominal voltage of the load.
Voltage feedback techniques generally used for the voltage regulation typically incorporate two voltage sensing loops, known as remote-sense and local-sense respectively. The remote-sense loop may provide a pair of sense lines (e.g., positive and negative lines) connected directly at the point of load for feedback information of the load voltage and the local-sense loop may be constructed in the power converter (e.g., at the terminal outputs the power converter) to provide feedback information in connection with the terminal voltage of the power converter.
Traditionally, it is known to use the remote-sense loop as the dominant control loop over the local-sense loop. For example, this technique allows the system to automatically switch to local regulation if the remote-sense lines were accidentally disconnected. This technique generally works well under normal operation or if the remote sense leads are accidentally removed. However, this feedback methodology has no provision to account for other failure modes, such as electrical open power lines or electrically shorted remote sense leads. Under such conditions the power converter may operate in an uncontrolled condition resulting in an undesirable high voltage output that can lead to system shutdown and/or failure of components.